1. Field of the Invention
The present invention relates to a heat sink. More particularly, the present invention relates to a heat sink used for diffusing heat generated by an integrated circuit package, in which heat is generated, such as a microprocessor unit incorporated into portable electronic equipment such as a notebook-type computer. Also, the present invention relates to a heat sink used for diffusing the heat generated by a hard disk device incorporated into portable electronic equipment.
2. Description of the Related Art
Recently, a microprocessor of high performance has been incorporated into a portable type electronic equipment for the purpose of increasing the processing speed and the processing capacity. A quantity of heat generated by this microprocessor is larger than the quantity of heat generated by other electronic parts. Therefore, the microprocessor by which a large quantity of heat is generated is locally air-cooled by a heat sink.
Concerning the heat sink used for locally cooling the microprocessor, there is provided a heat sink which is naturally cooled and further forcibly cooled for enhancing the cooling capacity in such a manner that a cooling fan is set on the naturally cooled heat sink. Also, in order to reduce the dimensions of the apparatus, as disclosed in Japanese Unexamined Patent Publication No. 6-268125, there is provided a heat sink in which a cooling fan is embedded.
However, the prior art disclosed in Japanese Unexamined Patent Publication No. 6-268125 is disadvantageous in that the height of the heat sink is increased because the heat sink into which the fan is incorporated is attached onto a heating component.
In order to solve the above problems, there is disclosed a technique in which a heating component is cooled by a heat sink in such a manner that the heating component is mounted at a position distant from the heat sink, and the heating component is connected with the heat sink by a heat pipe, and heat which has been generated by the heating component is transmitted to the heat sink via the heat pipe. In the above case, for example, it is possible to arrange the heating component and the heat sink in the transverse direction. Accordingly, the height of the apparatus can be reduced.
Even in the above prior art in which the heat pipe is used, it is necessary to improve the heat sink so that the cooling performance of the heat sink can be enhanced to diffuse a large quantity of heat generated by the heating component. In order to meet the above requirements, there is disclosed a technique in which a heat sink is combined with a cooling fan so that the heat sink can be cooled by means of forcible cooling in addition to natural cooling. When the heat sink is combined with the cooling fan according to the above prior art, a conventional fan is used, which is set on a conventional heat sink. A heating component mounted at a position distant from the heat sink is connected with the heat sink by a heat pipe. By this heat transmitting member, heat generated by the heating component is transmitted to the heat sink, and the heat sink is forcibly air-cooled by a cooling fan.
However, according to the above prior art in which the heat pipe is used, the cooling fan is placed upon the heat sink. Accordingly, it is necessary to provide a space into which the cooling fan is incorporated in addition to a space into which the heat sink is incorporated.
Further, in this example in which the heat pipe is used, the entire circumference of the heat pipe is surrounded by a bottom plate of the heat sink, and the diameter of the heat pipe is increased by the thickness of the heat sink. For the above reasons, a space in which the heat pipe is attached is increased within the height of the heat sink. Therefore, it becomes difficult to ensure a space in which the cooling fan is embedded in the heat sink. This space, in which the cooling fan is embedded, cannot be ensured in the heat sink. The cooling fan protrudes out of the heat sink. Therefore, it is impossible to reduce the thickness of the apparatus.
Even if the height of the heat sink is increased so as to embed the cooling fan in the heat sink, it is impossible to meet the requirements of a portable type information processor, the thickness of which has been increasingly reduced.
When the heat sink in which the cooling fan is embedded is mounted on the heating component, it is necessary to provide a space on the heating component into which the heat sink is incorporated. When it is attempted to mount the heat sink on the printed board on which the heating component is mounted, it is impossible to ensure a space into which the heat sink is incorporated because the density of mounting parts on the printed board has been increased.